This invention relates to a method for manufacturing a filled hollow fibre composite material and to a material made by the method.
Hollow fibre glass composite materials have been proposed which can be fabricated using prepreg hollow fibre material. The properties of such a composite material can be altered by filling the hollow fibres with a suitable material. It has been proposed that the hollow fibres of individual hollow fibre composite material plies be filled before the plies are made up one upon the other, which laid up plies are then treated in an autoclave at high pressure and high temperature. This exposure to high pressure and high temperature could degrade the filling in the hollow fibres which would be detrimental to the properties of the resulting composite material particularly if the filling material in hollow fibres in different plies in the prepreg lay-up is different with different resistance or tolerance for high temperature and high pressure conditions. This can result in an uneven deterioration through the thickness of the resulting composite material which could give rise to a product of uncertain properties.
There is thus a need for a generally improved method for manufacturing a filled fibre composite material which minimises deterioration during the manufacturing process of the materials utilised in the composite material and hence minimises undesirable variation in the resulting product.
According to a first aspect of the present invention there is provided a method for manufacturing a filled hollow fibre composite material including the steps of:
laying up a plurality of prepreg plies of hollow fibre composite material and non-stick film material one on top of another with the non-stick film material interleaving successive plies at selected areas thereof,
treating the laid up interleaved plies to resin bond together the ply areas not interleaved with the non-stick film material to form a hollow fibre composite material laminate in which the interleaved areas remain unbonded together,
treating edge regions of the laminate to expose open unfilled hollow fibre ends,
separating the plies at the non-stick film material in the unbonded interleaved areas to provide access to the open hollow fibre ends in each ply and,
introducing a film material or materials having desired properties different from that of the hollow fibre material, into the hollow fibres through the open hollow fibre ends in one or more of the separated plies in the unbonded interleaved areas to form a filled hollow fibre composite material.
Preferably the resin bonding treatment step is effected in an autoclave.
Conveniently the laminate edge region treatment step includes dry cutting off edge regions of the laminate in both unbonded interleaved areas and bonded areas to remove hollow fibre ends filled with resin during resin bonding to leave cut edges on laminate exposing unfilled hollow fibre ends, grinding and polishing the laminate cut edges in a liquid coolant to remove resin smeared over the open unfilled hollow fibre ends by the dry cutting, ultrasonically cleaning the ground and polished laminate cut edges and there with the open unfilled hollow fibre ends, in a liquid solvent and drying the cleaned laminate cut edges.
Advantageously the hollow fibre composite material utilised is a resin bonded ply of hollow glass or carbon fibres.
Preferably the non-stick film material utilised is a sheet of plastics material coated with a release agent.
Conveniently the filler material utilised is in liquid powder and/or particulate form.
Advantageously grinding and polishing is carried out with silicon carbide paper.
Preferably the liquid coolant utilised in grinding and polishing is water.
Conveniently the liquid solvent utilised in ultrasonic cleaning is dichloromethane.
Advantageously ultrasonic cleaning is carried out for substantially two hours.
Preferably drying is carried out at substantially 90xc2x0 C. for substantially ten minutes.